This type of harness is used to serve a plurality of different destinations from a common point referred to as the "point of origin". Such a harness is used in particular for supplying power and/or data/dialog to the various members of a system from the point of origin. The harness has a network of conductors co-operating together to define both a trunk starting from the point of origin and various branches leading off from the trunk. The branches correspond to the different destinations, and they are connected to the different members of the system. They define forks along the trunk, and may in turn have bifurcations for the purposes of connecting them to the various members.
The structure of this type of harness is such that it has a trunk and thin branches leading off from the trunk, the diameter of the trunk being large where it starts from the point of origin, and decreasing going away from the point of origin at each branch. The forks at which the branches lead off from the trunk define successive segments therealong, the end segment at the opposite end from the point of origin forming the last branch of the harness.
The ratio between the diameters of the two end segments is often high, and frequently greater than 20. The branches may in turn have different numbers of conductors from one another, and therefore have different diameters. Their diameters are much smaller than the diameters of the respective segments from which they start.
In a good many applications, such harnesses need to have high-performance protection against electromagnetic interference, and need to be strong enough to withstand considerable shocks, vibrations, and heat and/or chemical attack, in particular. This is particularly important when they are used in land, air, or sea mobiles.
Independently from the problem of providing high-performance electromagnetic protection, the use of braiding is known for covering a network of conductors, mainly to provide cohesion therefor or to improve the overall strength thereof. Such braiding leaves the network relatively easy to handle so as to facilitate laying it and inserting it to the various points at which its branches are connected in the mobile in which it is used.
The overall-strength braiding is often a textile fabric, or is sometimes made of metal. In general, it provides the network with good mechanical properties, but cannot per se directly provide high electromagnetic protection, in particular at the forks.
To obtain high electromagnetic protection for the harness, two possible techniques are known for shielding the substantially linear portions, and for providing continuity in the protection at the forks.
A first one of those techniques consists in using segments of cable which correspond to the segments and to the branches of the network, and which are initially independent and shielded individually by means of metal braiding, and in connecting them together by means of shielded splice boxes. The network is thus made up at the same time as the forks are shielded, by means of the splice boxes.
The shielded network obtained by using the first technique offers excellent electromagnetic performance levels, due both to the uniformity of the initial shielded segments of cable, and to the low transfer impedance due to the splice boxes. The network also has generally satisfactory mechanical properties. However, it is heavy, expensive, bulky, complex, and inflexible, due to it being made up from shielded cables which are different from one other, and from splice boxes which are also different from one another.
The second technique consists in using a network of conductors defining the harness directly, in shielding the branches and the various segments of the trunk by means of metal shielding braids made previously and threaded over each of them, and in threading heat-shrinkable metal-plated sleeves over the various forks to provide continuity in the shielding with the above-mentioned braids.
The shielded harness made by using the second technique is lighter in weight, less expensive, more compact, simpler, and more flexible than the harness made by using the first technique. However, with the second technique, the electromagnetic performance levels of the harness are poor and often insufficient, as are its mechanical properties, in particular its ability to withstand vibration which, as a result, reduces the electromagnetic protection provided.
The shielding method used in the second technique is difficult to perform, and even almost impossible when the herringbone harness has a large number of branches, and therefore has very large ratios between the diameters of the different segments, or between the diameters of the segments closest to the point of origin and the corresponding branches.
Furthermore, independently from the electromagnetic shielding of the network of conductors, and from the continuity in shielding over the forks, those two techniques require end connectors to be connected subsequently to the harness, at the ends of the various branches, and at the known common point of origin, and electromagnetic protection to be provided at the rear connection ends of the connectors. Mounting and electromagnetically protecting the connectors involves handling the shielding braids of the branches and of the starting trunk roughly, so as to thread them over the rear end of each corresponding connector, and then to lock them thereon.
Such rough handling irretrievably degrades the shape of the braids, and does not enable satisfactory continuity in shielding to be obtained between the connectors and the network of conductors, at least for some uses of the harnesses.
An object of the present invention is to avoid the drawbacks of those known techniques, so as to provide a shielded "herringbone" harness having high electromagnetic performance levels and high mechanical strength.